Obstructive Sleep Apnea (OSA) is a condition characterised by repetitive obstruction of the upper airway often resulting in oxygen desaturation and arousals from sleep. The classic daytime manifestation is excessive sleepiness but other symptoms such as unrefreshing sleep, poor concentration and fatigue are commonly reported (Sleep-Related Breathing Disorders in Adults-AASM Task Force, Sleep 22, 1999)
The use of nasal continuous positive airway pressure (CPAP) to treat OSA was taught by Sullivan in U.S. Pat. No. 4,944,310. Other developments are taught in U.S. Pat. Nos. 5,704,345; 6,029,665 and 6,363,933.
Nasal CPAP systems typically comprise a flow generator, air tubing, and a patient interface (for example, a nasal mask). The flow generator provides a supply of air at positive pressure.
A variety of mask systems are known for use in treating sleep disordered breathing (SDB), such as the BUBBLE® mask, MIRAGE®, ULTRA MIRAGE®, and MIRAGE VISTA™ masks, all manufactured by ResMed Limited.
Another known mask is the Weinmann nasal mask.
A mask system typically comprises headgear and a mask assembly. The headgear is used to hold and position the mask on the face of a patient. The mask assembly typically comprises at least a rigid shell and a soft face-contacting cushion. Some mask assemblies also include elbows, vents, headgear clips, forehead supports.
A number of cushions have been patented, for example see U.S. Pat. Nos. 6,112,746; 6,357,441; 6,513,526; as have forehead supports (See U.S. Pat. Nos. 6,119,693; 6,463,931; 6,520,182; 6,532,961), headgear connectors (U.S. Pat. No. 6,374,826), mask ports (U.S. Pat. No. 6,439,230), and cushion clips (U.S. Pat. No. 6,412,487). For example, U.S. Pat. No. 6,513,526 discloses both nasal and full face cushions. The contents of all these patents are hereby incorporated by cross-reference.
Another known mask assembly the PAPILLION™ mask, manufactured by MAP, Germany is shown in Austrian Design Registrations #50770 and #50771 (and U.S. Design Pat. D484,237 and Australian Design Registration Application 2153/2002).
Since mask systems for treating sleep disordered breathing have to be worn for several hours every night while a patient sleeps, designers strive to make them comfortable. In particular, they strive to attempt to eliminate the mask system being a source of pressure sores on a patient's face.
A problem which can occur in prior art mask systems is that there can be drag forces from the tube which when transferred through the elbow can disrupt the seal of the cushion on the face.
One solution to this problem is found in U.S. Pat. No. 6,039,044. It is an aspect of the invention to provide at least an alternative solution to this problem.
A difficulty with some prior art mask assemblies is that those which achieve a clinically effective seal while being comfortable to wear each night at home can be expensive to manufacture. Headgear can represent a significant proportion of the cost of manufacturing a mask system. The manufacturing costs are passed onto customers which leads to a more expensive mask assembly for patients. This may in turn mean that fewer patients can afford treatment. This may also mean that there can be a tendency for clinics and hospitals to reuse masks among numerous patients. Unless thorough hygiene systems are put in place to manage cross-infection it is not advised that a mask be re-used by different patients. In general, particularly in hospitals with the advent of respiratory diseases such as SARS, it is desirable to have a mask system which is cheap enough to be disposable.
It is a further aspect of the invention to provide a low cost mask assembly for treating sleep disordered breathing.
It is a further aspect of the invention to provide a disposable mask assembly for treating sleep disordered breathing.